1. Field of the Invention
The present invention relates to a process for removing an organic toxicant from an aqueous waste stream using a polymeric adsorbent. More particularly, the present invention relates to a process for selectively removing specific organic toxicants from aqueous waste streams associated with the production of petroleum and petroleum products by contacting such waste streams with a non-ionic macroreticular polymeric resin.
2. Description of the Related Art
Wastewater produced by certain industrial processes often contains toxic materials that are unique to the particular industry involved. Each industry, therefore, seeks to employ the most effective and economical methods available to treat or remove the particular toxicants found in that industries' effluent wastewater.
In the petroleum industry, a number of methods are currently used to render contaminated wastewater suitable for discharge, including microbial biodegradation and treatment with activated carbon. The treated effluent produced by these processes is typically monitored to determine its suitability for discharge. One increasingly important method of monitoring effluent toxicity uses a bioassay technique in which an indicator species, such as a species of fish known to be sensitive to certain toxicants, is exposed to the treated wastewater to determine if the water contains any residual toxicity. In recent years, such bioassays have become more stringent by using indicator species which are increasingly sensitive to the presence of very low levels of aquatic toxicants.
Using such bioassay techniques, aqueous waste streams associated with the production of petroleum and petroleum products have recently been found to be toxic to certain highly-sensitive species of indicator fish. We have discovered that this toxicity is caused by a specific group of organic materials. These newly-discovered organic materials are present in aqueous waste streams at extremely low levels. However, even at concentrations of less than 10 parts per billion, these materials are highly toxic to the indicator species of fish. Thus, aqueous waste streams containing these materials must be treated prior to discharge to reduce the concentration of these toxicants to an acceptable level.
These newly-discovered organic toxicants do not appear to be readily biodegraded under the conditions currently employed to treat aqueous petroleum waste streams. More costly effluent treatment using activated carbon has been found to reduce the concentration of these toxicants to acceptable levels, however, activated carbon is not selective for these specific toxicants and removes most organic matter present in the waste stream. Thus, the use of activated carbon to remove these specific organic toxicants is both inefficient and uneconomical.
Therefore, a new method or process is required to selectively remove these newly-discovered organic toxicants from aqueous waste streams.
The use of non-ionic polymeric adsorbents to treat industrial waste effluents has been described previously. For example, R. Kunin in Polymer Engineering and Science, 17, 58 (1977), describes the use of non-ionic macroreticular resins, such as AMBERLITE.RTM. XAD resins, to treat aqueous industrial wastes containing phenol or various organic acids, bases and neutral organic compounds. R. A. Moore and F. W. Karasek in Intern. J. Environ. Anal. Chem., 17, 187 (1984), also discuss the extraction of organic compounds from aqueous media by AMBERLITE.RTM. XAD resins.
Similarly, D. C. Kennedy in Ind. Eng. Chem. Prod. Res. Develop., 12, 56 (1973), describes the adsorption of phenols and chlorinated hydrocarbons from aqueous solutions using AMBERLITE.RTM. XAD-4. Also discussed is the use of AMBERLITE.RTM. XAD-8 to decolorize kraft pulp mill effluents.
Bleached kraft effluents have been shown by I. H. Rogers in Bimon. Res. Notes Can. Forest. Serv., 28(4), 24 (1972), to contain organic components which are toxic to sockeye salmon fry (Oncorhynchus nerka). These toxic components were recovered from the kraft mill wastes using AMBERLITE.RTM. XAD-2 resin. Rogers later reported in J. Am. Oil Chemists' Soc., 55, 113A (1978), that the main toxic components of bleached kraft effluents are terpenoid resin acids such as abietic acid, dehydroabietic acid, isopimaric acid, palustric acid and pimaric acid. Such terpenoid resin compounds are not believed to be the cause of the toxicity discussed herein.
U.S. Pat. No. 3,531,463, issued Sep. 29, 1970 to R. L. Gustafson et al., discloses a process for separating a dissolved water-soluble organic substance having a hydrophobic portion and a hydrophilic portion from an aqueous medium by contacting the medium with particles of an essentially non-ionogenic, macroreticular water-insoluble cross-linked polymer.
U.S. Pat. No. 3,803,030, issued Apr. 9, 1974 to R. A. Montanaro et al., discloses a process of removing contaminants, such as color bodies and metals, from a liquid medium using a solvent-regenerable macroreticular polymer resin.
U.S. Pat. No. 3,853,758, issued Dec. 10, 1974 to M. J. Hurwitz et al., also teaches that effluents from dye manufacturing and dyeing operations can be decolorized by using a combination of a primary polymeric adsorbent composed of a non-ionogenic macroreticular adsorbent and a secondary adsorbent comprising a weak-electrolyte ion exchange resin to remove the color bodies.
U.S. Pat. No. 4,297,220, issued Oct. 27, 1981 to E. F. Meitzner et al., discloses a method for adsorbing an organic material from a fluid or fluid mixture using a macroreticulated crosslinked copolymer.
Similarly, U.S. Pat. No. 4,399,274, issued Aug. 16, 1983 to R. T. Goegelman et al., describes a process for isolating and separating non-ionic lipophilic substances, specifically avermectin compounds, from solution in water, organic solvents or miscible mixtures thereof using an insoluble synthetic resin which is an addition copolymer having a cross-linked structure.